Why does it say "ha'Lo At Hi ha'Machareves Yam"?
Malbim: You did so Yourself; we did not have merit. Keri'as Yam Suf was Chesed, with Your Zero'a 1 .
It says "va'Yar Yisrael Es ha'Yad ha'Gedolah" (Shemos 14:31). According to Malbim, it should say Zero'a! This requires investigation. (PF)
Why does it say "ha'Machareves Yam", "Mei Tehom Rabah", and "Ma'amakei Yam"?
Radak: The matter is repeated three times in different words. All refer to Keri'as Yam Suf.
Malbim: There were two miracles in Keri'as Yam Suf. (a) Hashem dried the sea. (b) He made the depth into a level path for Yisrael to pass through.
What is the tense of "ha'Samah"?
Radak: It is past tense, for the accent is on the penultimate syllable. It is as if it says Asher Samah. Also "ha'Ba'ah Mitzraimah Shiv'im" (Bereishis 46:27) is like Asher Ba'ah. The prefix Hei ha'Yedi'ah (to identify) does not come with the past tense.